1. Field of the Invention
The present invention relates to Short Message Service (SMS) in a private branch exchange (PBX), and more particularly, to a PBX system and a service method by which SMS messages received via a main line are distributed to extension units.
2. Description of the Related Art
In general, a PBX is a small sized exchange system to switch and connect extension calls in a specific zone, and widely used for intercommunication in a company or office. At present days, mobile communication service users have been rapidly increased, and subscribers using a mobile communication even in a company also have been increased.
Accordingly, there has been introduced a wireless PBX which has a mobile communication function to provide a private mobile communication service to mobile units existing in a specific zone such as a company.
A wireless PBX includes a Base Station Controller (BSC) and a Mobile Switching Center (MSC) to provide a wired/wireless exchange service to mobile extension units in order to realize a wireless PBX service. Then, in a service zone of the wireless PBX, subscribers can call any mobile extension units registered to the wireless PBX free of charge.
In the meantime, a Short Message Service (SMS) may be referred to as an individual subscriber service since it is provided to individual units. In case that several subscribers share a single unit, sub-addresses can be used to identify the individual subscribers from one another. However, these are serviced only to home telephones, and the PBX provides the Short Message Service (SMS) as an internal function thereof.
In case of a Short Message Service (SMS) received at the same number, it is possible to identify actual receivers by using ten sub-addresses from 0 to 9. However, since a number of subscribers share the same main or office line, only ten sub-addresses are not sufficient for the PBX to provide a satisfactory service. For example, when twenty PBX subscribers use the same main line, only ten subscribers can be serviced even if sub-addresses are provided from a Short Message Service Center (SMSC). Because of these restrictions, a conventional PBX can hardly provide an SMS in practice.